This invention relates to a ball feeding device for feeding numerous balls, such as balls for ball bearings, pearls or resin balls, one by one to select non-defective balls or to manufacture ball bearings or pearl necklaces.
As is well-known in the art, balls used for ball bearings have to have substantially uniform diameters. Their tolerance is 10 .mu.m, which is very harsh. Thus, after producing numerous balls, it is necessary to select only those balls having diameters within the above tolerance.
FIG. 13 schematically shows the structure of a ball sorter of this type. This device comprises two cylinders 101, 102. A gap is defined therebetween which expands gradually from one end of the cylinders to the other end. Balls 103 are rolled along the gap from its narrow end. Once each ball 103 rolling along the gap reaches a point where the gap diameter is slightly larger than that of the ball, it falls through the gap between the cylinders 101, 102. Thus, one can tell the diameter of each ball by checking the point at which the ball falls. Balls are thus sorted in this manner.
On the other hand, in order to sort balls, numerous balls have to be guided one by one onto the gap between the cylindrical members. A ball feeding device for guiding balls is used in combination with the above ball sorter.
In conventional ball feeding devices of this type, balls are guided one by one by vibrating them. Namely, numerous balls are vibrated microscopically to move them little by little until they are arranged in a line. The aligned balls are then fed one by one.
But this type of conventional ball feeding device has a drawback in that, since many balls are vibrated at a time, they tend to damage, chip or deform each other when they collide with each other. Also, by vibrating the balls, they tend to be magnetized or electrostatically charged, so that they may be chained together. This makes it impossible to feed balls one by one and thus to sort balls accurately.
An object of this invention is therefore to feed numerous balls one by one without allowing many impacts on the balls and without the balls being magnetized and electrostatically charged.